This invention is directed to a 360.degree. electronically scanned sonar and in particular to a sonar having a thinned transducer array.
Conventional volume scanning sonars have transducers in which the array elements are arranged in some type of cylindrical configuration having a matrix of rows (layers) and columns (staves) in which the elements are spaced .lambda./2 apart. U.S. Pat. No. 3,409,869 which issued to McCool et al. on Nov. 5, 1968 describes such a transducer. In order to scan horizontally and/or vertically with such a transducer, a control system energizes the elements in the array at predetermined times forming a beam which is scanned either horizontally or vertically. U.S. Pat. No. 3,859,622 which issued to Hutchison et al. on Jan. 7, 1975, describes an electronic scanning switch for beam forming in sonar systems, and U.S. Pat. No. 4,001,763 which issued to Kits van Heyningen on Jan. 4, 1977 describes a further electronically stabilized beam former system for a cylindrical type array in which the transducer is also curved in the vertical direction.
The cost for a large full array sonar transducer can be reduced somewhat by eliminating some of the elements in the array in order to form a thinned array. In linear antenna arrays of the type described in U.S. Pat. No. 3,780,372 which issued to Unz on Dec. 18, 1973 or U.S. Pat. No. 4,071,848 which issued to Leeper on Jan. 31, 1978, the elements are nonuniformily spaced at what is considered to be optimal non-periodic positions in the array.